Detecting infectious diseases in people, such as Severe Acute Respiratory Syndrome (SARS), is an invaluable first step toward preventing the spread of such diseases. Infectious diseases may be easily spread in high traffic areas such as airports and workplaces and are difficult to detect given the busy activity and divergent travel paths or people is such places. Recent efforts to control the spread of SARS, as well as other infectious diseases, have prompted public health officials to develop a rapid screening process to detect individuals who are experiencing the specific symptom of an elevated body temperature that is common to several infectious diseases. If individuals who exhibit an elevated body temperature, i.e., a fever, may be identified prior to boarding an airplane or entering a factory floor, further health screening can be conducted on only the identified individuals thereby saving both time and effort otherwise wasted by further health screening of healthy individuals.
Because high fever is a symptom of SARS and other infectious diseases, health screening systems of the past have used thermal imaging cameras as a means to rapidly identify potential individuals exhibiting an elevated temperature as the individual passes through a checkpoint. In an effort to identify persons potentially carrying an infectious disease, health care officials in several locations worldwide have employed thermal imaging cameras to attempt to measure and analyze the skin temperature of individuals passing through high-risk regions. Individuals exhibiting elevated skin temperatures are then isolated for further evaluation to determine the cause.
FIG. 1 is a block diagram of a conventional thermal detection system 100 that may be used for detecting elevated skin temperatures, or other thermal anomalies, that may be present within person 101 passing through a screening area. The system 100 includes a thermal imaging camera 110 that monitors a screening area through which a persons 101 to be screened pass regularly. Thermal images 151 of the individual may be captured by the thermal imaging camera 110 and displayed on a monitor 150. The display of the thermal images 151 can be calibrated such that the slightest temperature deviation above or below a normal human body temperature (98.6° F.) is displayed on a monitor 150 being watched by a health screener (not shown) in an effort to identify possible carriers of infectious diseases. As a result, the health screener may request that persons exhibiting a temperature above normal to go through additional health screening to determine the cause.
The thermal detection system 100 utilizes the nature of thermal radiation and thermal imaging in that all objects above Absolute Zero (0 Kelvin) emit at least some infrared radiation. While infrared radiation is invisible to the human eye, it can be detected and displayed by the thermal imaging camera 110. The thermal imaging camera 110 detects the infrared radiation emitted by an object and converts it into a monochromatic or multi-colored image on the monitor 150 wherein the various shades or colors represent the thermal patterns detected. If calibrated to human body temperature range, any object exhibiting radiation corresponding to temperatures beyond 98.6° F. may be displayed in shades of yellows, oranges, and reds consistent with how much higher in temperature the object is than the calibrated baseline. Likewise, any object exhibiting radiation corresponding to temperatures below 98.6° F. will be displayed in shades of blues, greens, and purples consistent with how much lower in temperature the object is than the calibrated baseline.
For example, a person 101 not having a fever (i.e., the person's skin temperature is a normal 98.6° F.) will be displayed on the monitor 150 as a neutral color (such as white) while the person's clothing or hair will appear blue, green, or purple. If the person 101 does, in fact, have a high fever, the person's exposed skin (the person's forehead, in particular) will tend toward the shades of yellow, orange, and red as the temperature of their skin is typically above the calibrated baseline. Thus, a health screener watching the monitor 150 may identify a person 101 running a fever and isolate that person 101 for further health screening.
Several problems are associated with the conventional thermal detection system 100 of FIG. 1. In particular, one problem is that the health screener must remain diligent in looking for color deviations on the monitor 150 indicating higher temperatures. Thus, if the person 101 being screened is carrying a hot cup of coffee, the coffee cup may appear yellow, orange, or red and the health screener will have to distinguish in the image between the coffee and other areas corresponding to a person's exposed skin or face. Any number of other objects may also appear in yellow, orange, or red due to the objects exhibiting temperatures above the calibrated baseline temperature (e.g., laptop computers, cell phones, hamburgers, etc.) that also must be distinguished by the health screener watching the monitor 150. As a result, the health screener must remain all the more diligent in a busy screening area.
Other problems of the conventional thermal detection system 100 include the requirement of several frames of data captured by the thermal imaging camera 110 in order to process temperature data accurately. Obtaining accurate temperature with such conventional systems 100 requires that the person 101 remain stationary for up to several seconds while data is collected. Further, the thermal imaging camera 110 may have accuracy limitations for temperature measurement. Typical accuracy specifications for temperature measurement are ±2% of target temperature or ±4° F., whichever is greater. With this in mind, a person 101 with a normal body temperature of 98.6° F. may be displayed as high as 102° F. (fever) while a person with an actual fever of may be displayed as low as 95° F. (below normal temperature).
Yet another problem is that a health screener's attention may be distracted to the point that a person having a fever is actually missed by the health screener as human error is always a factor. Other problems include a person wearing a hat not properly being screened, a person's face being turned away from the thermal imaging camera while traversing the screening area, and human mistakes being made by the health screener due to misinterpretation of the thermal images. In short, the conventional thermal detection system 100 of FIG. 1 is replete with possible failure points due to human error which results in a poor health screening system when dealing with such contagious diseases like SARS.